1. Field of the Invention
The present invention relates to a high frequency circuit module and a communication device such as a mobile wireless terminal and a pocket telephone employing the same.
2. Description of the Prior Art
The miniaturization and the enhancement of the efficiency of power of a high frequency circuit module used for a mobile wireless terminal, a pocket telephone and others in view of the mountability and talk time have been important objectives.
For a high frequency circuit module used for a communication device such as conventional type mobile wireless terminal and pocket telephone, the one using a single layer or multi-layer dielectric substrate is known.
An example of a high frequency circuit module using a single layer dielectric substrate is shown in the proceeding of the 1996 Institute IEIC Spring Conference C-86, xe2x80x9cA Power Amplifier Using Single Layer Alumina Substrate with Thin-Film Resistors and Capacitors for North American Digital Phone Systemxe2x80x9d (hereinafter called first conventional technique). According to the first conventional technique, a transmission line which is a distributed element, a lumped constant element such as a resistor, a capacitor and an inductor and a semiconductor element are formed on the same surface of a dielectric substrate to compose an input-output matching circuit and a power amplifier. A high frequency signal is transmitted to an external device by a high frequency signal electrode provided to the surface of the dielectric substrate. The earth electrode of the semiconductor element provided to the surface of the dielectric substrate and an earth electrode on the reverse side are connected via a through-hole.
Also, an example of a high frequency circuit module using a multi-layer (two-layer) dielectric substrate is shown in the proceeding of the 1997 Institute IEIC Conference Electronics Society C-2-14, xe2x80x9c1.9 GHz RF Front-End Module Using a Ceramics Substratexe2x80x9d (hereinafter called second conventional technique). According to the second conventional technique, a transmission line which is a distributed constant element, an input-output matching circuit composed of a lumped constant element such as a resistor, a capacitor and an inductor and a semiconductor element are formed on the same surface of a dielectric substrate to compose a high frequency circuit module. A high frequency signal electrode provided to the surface of a first layer of the dielectric substrate and a high frequency signal electrode on the reverse side of a second layer are connected via wiring provided to the surface of the second layer through a through-hole. The earth electrode of the semiconductor element provided to the surface of the first layer of the dielectric substrate and an earth electrode on the reverse side are connected via a through-hole. The order of the layers of the dielectric substrate are counted as a first layer, a second layer, a third layer, etc., from the surface to the reverse side.
Referring to FIGS. 9 to 11, relationship between the miniaturization and the enhancement of the efficiency of power in the first conventional type technique will be described below.
FIG. 9 is a general schematic sectional view showing a transmission line formed on a single layer dielectric substrate. A conductor 43 on the surface, a dielectric substrate 44 and ground metal on the reverse side 45 forms a transmission line.
FIG. 10 shows calculated values of transmission loss at the frequency of 1.9 GHz when the relative dielectric constant of the dielectric substrate 44 is 8.1 and the thickness of the dielectric substrate 44 is varied from 0.1 mm to 3.0 mm. Curves 1 to 3 show cases in which the width of the conductor 43 forming a transmission line is respectively 0.1 mm, 0.2 mm and 0.5 mm. As clear from FIG. 10, in the cases of any width of the conductor 43, as the dielectric substrate 44 becomes thick, the transmission loss has a tendency to become small.
FIG. 11 shows calculated values of transmission loss at the frequency of 1.9 GHz when the relative inductivity of the dielectric substrate 44 is 8.1 and the width of the conductor 43 forming a transmission line is varied from 0.02 mm to 3.0 mm. Curves 1 to 3 show cases in which the thickness of the dielectric substrate 44 is respectively 0.15 mm, 0.3 mm and 0.6 mm. As clear from FIG. 11, in the cases of any thickness of the dielectric substrate 44, the transmission loss decreases as the conductor 43 forming a transmission line becomes wide, becomes minimum in a range in which the width of the conductor 43 is 0.3 to 0.7 mm and increases when the conductor 43 becomes wider.
As clear from the above description, to reduce transmission loss, it is required to thicken the dielectric substrate 44 and widen the conductor 43 and the miniaturization of the high frequency circuit module has a limit.
Next, referring to FIGS. 12 to 14, relationship between the miniaturization and the enhancement of the efficiency of power in the second conventional type technique will be described.
FIG. 12 is a general schematic sectional view showing a transmission line formed on a two-layer dielectric substrate. A conductor 46, a dielectric substrate 47, ground metal 48 on the reverse side and ground metal 49 on the surface forms a transmission line.
FIG. 13 shows calculated values of transmission loss at the frequency of 1.9 GHz when the relative dielectric constant of the dielectric substrate 47 is 8.1 and the thickness of the dielectric substrate 47 is varied from 0.1 mm to 3.0 mm. Curves 1 to 3 show cases in which the width of the conductor 46 forming a transmission line is respectively 0.1 mm, 0.2 mm and 0.5 mm. As clear from FIG. 13, in the cases of any width of the conductor 46, as the dielectric substrate 47 becomes thick, the transmission loss becomes small.
FIG. 14 shows calculated values of transmission loss at the frequency of 1.9 GHz when the relative inductivity of the dielectric substrate 47 is 8.1 and the width of the conductor 46 forming a transmission line is varied from 0.02 mm to 3.0 mm. Curves 1 to 3 show cases in which the thickness of the dielectric substrate 47 is respectively 0.15 mm, 0.3 mm and 0.6 mm. As clear from FIG. 14, in the cases of any thickness of the dielectric substrate 47, as the conductor 46 forming a transmission line becomes wide, the transmission loss has a tendency to become small.
As clear from the above description, to reduce transmission loss, it is required to thicken the dielectric substrate 47 and widen the conductor 46 and the miniaturization of the high frequency circuit module has a limit.
The object of this invention is to provide a high frequency circuit module which can be more miniaturized and a communication device using it.
To achieve the object, a high frequency circuit module according to this invention uses a two or more-layer dielectric substrate and the thickness of the dielectric substrate between a conductor forming the transmission line of a matching circuit on the side of input or output and ground metal is composed of two or more layers.
Specifically, to thicken a dielectric substrate that ranges between the conductor forming the transmission line of the matching circuit on the side of input or output and the ground metal, the ground metal provided to the dielectric substrate between them is formed in the shape in which a part is hollowed out so that a part opposite to the conductor is included.
As a required part can be thickened without varying the thickness of the whole dielectric substrate, the transmission loss can be reduced, and a high frequency circuit module and a communication device using it can be miniaturized.
The above-mentioned and others features and objects of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings.